The present invention relates to a welding slot sealing structure and its welding method.
For an impeller attached to a centrifugal compressor or the like, welding is generally used when a blade is joined to a shroud. In manufacturing the impeller by welding, the height and shape of blade are restricted.
For example, to manufacture an impeller that cannot be reached by hand and can not be welded, such liquid phase diffusion bonding as described in JP-A-5-202701 and JP-A-6-272696 may be used. Also, when an intricately-shaped impeller is manufactured, laser slot welding may be performed.
In these welding processes, a shroud or a disk, to which the blade is welded, is formed with a slot in the surface on the opposite side from the blade, and a laser beam is applied from the slot side to melt and weld the shroud or disk and the blade. This method, however, requires overlaying work such that the slot is filled with powder, which is melted by the laser beam applied while the powder is being charged, after the blade has been welded to the shroud or the disk. This is because the fluid performance of impeller is degraded remarkably if the slot is left as it is.
According to the above-described related art, when the slot, which has been formed in the shroud or the disk to perform laser welding, is filled by overlaying after the blade has been welded to the shroud or the disk with the laser beam, thermal distortion may be caused by the overlaying. Also, if the slot is left as it is, a problem of degraded fluid performance arises.